This is the 4715th most frequent German word.
wahrscheinlichste
Most probable.
Here the word 'wahrscheinlichste' is used in its superlative form to emphasize the highest degree of probability among available options.
Das ist die wahrscheinlichste Möglichkeit, die wir haben.
That is the most probable option we have.
In this sentence, 'wahrscheinlichste' indicates the answer with the highest likelihood or probability among others.
Die wahrscheinlichste Antwort könnte sein, dass es so geplant war.
The most likely answer could be that it was planned that way.
This usage highlights 'wahrscheinlichste' as describing the theory most supported by evidence or appearing most plausible.